The conventional practice of pressure bonding includes passing a pair of strips in superimposed condition between a pair of abutting rolls which rotate in opposite directions with an equal peripheral speed, thereby integrally bonding the strips together under the influence of the pressure applied by the rolls. However, according to this procedure, the draft of each strip is uniquely determined by the resistance to deformation, the diameter of each roll or the load per unit area of each strip, and hence it is necessary to change the ratio of diameters of the abutting rolls in order to adjust the draft of each strip, which is a toublesome operation.